While the symbolic trailing raincloud over one’s head signifies a bad day, Italian architectural firm Carlo Ratti Associati recently unveiled an energy-efficient “personal cloud” for cooling off passersby in hot climates.

The Cloud Cast comprises a ceiling-mounted canopy of thin aluminium jets, each one equipped with an ultrasonic sensor for detecting motion à la whale-to-whale communication. An ultrasound signal is sent and if an echo is received in a given window of time, the object is deemed sufficiently near and hydro-valves in the spray jet activate to lightly mist the passerby. The sensors track your movement and direct the spray accordingly as you move, so that the whole system need not be triggered at once.

Soft, colored LED lights flash when the system is motion-activated. Evaporative cooling has been used for centuries in the Arabian peninsula and is more energy-efficient than air conditioning, as mist generators don’t do any of their own cooling. Rather, clouds of mist cool the surrounding air as they evaporate. Ratti developed the Cloud Cast while conducting research at the Massachusetts Institute of Technology, where he is director of the SENSEable City Lab.

While conventional misting systems are not sensitive to whether or not a room or outdoor area is populated, the Cloud Cast is predicated on only-as-needed use. “In traditional systems a lot of energy and water are consumed for cooling outdoor spaces, even when sparsely used,” Ratti told Mother Nature News Network. “In our project, we focus on misting people, gaining order of magnitudes in efficiency.” The new technology was created for and unveiled at the Museum of Future Government Services as part of the UAE Government Summit in February, and will be available commercially in the near future.